1. Technical Field.
This invention relates to an improved encapsulated lipid animal feed and the process for producing such feed in a commercially viable manner. One aspect of this invention relates to the composition of animal feeds produced by using plant and animal proteins, including but not limited to animal blood, fish protein, microbes such as algae, and abattoir waste-stream proteins. Another aspect of this invention relates to the method of precisely manipulating pH levels to optimize capsule strength and durability and minimize the quantity of exogenous chemical use. A final aspect is the method for shearing and mixing the ingredients in such a way that no air is entrained in the emulsion and complete shearing occurs allowing complete encapsulation of the lipid materials so as to enable large-scale commercial production that is economically practical.
2. Related Art.
The benefits of using protein-encapsulated lipid material in the production of animal feeds are well documented. In its dry form, the encapsulated lipid can be easily handled and packaged and, in the case of ruminant animals, it can pass through the rumen and be digested within the abomasum and lower gut of the animal. A number of patents have been issued on methods to achieve such encapsulation, for example, in U.S. Pat. Nos. 4,042,718; 4,138,505; 4,217,370; 4,225,620; 4,808,429; and 4,824,679. However, in the resulting mixtures using these disclosed methods, wherein agents are added to solubilize the proteinaceous material and to subsequently adjust the pH downward, the methods produce entrainment of air and incomplete shearing during the production of the emulsion. Entrainment of air promotes rancidity, fragile capsules and degradation of the encapsulated product. Additionally, the methods discussed above require large quantities of exogenous chemicals to accomplish the encapsulation. Consequently successful commercialization of the general encapsulation techniques covered by the above-listed patents has not been widely accomplished.
In Rawlings et al., U.S. Pat. No. 4,217,370 there is described a process which involves forming an emulsion of globules of nutrient lipid with an aqueous proteinaceous medium (e.g. blood) at a pH of between 9.0 and 13.0 and thereafter lowering the pH of the emulsion to its isoelectric point so as to aggregate the protein and simultaneously microencapsulate the lipid.
I have found that not all pH levels in the 9.0 to 13.0 range produce a strong capsule, nor does lowering the pH only to its isoelectric point. In some instances pH levels in the 9.0 to 13.0 range partially or completely break down the primary structure of the protein, making it impossible to achieve successful encapsulation of the lipid.
Further, the mixing devices prescribed in that patent entrain air in the mixture and are unable to produce a good dispersion/emulsion of lipid material within the rapidly-gelling alkaline blood. The Rawlings process also requires the addition of significant amounts of water to solubilize the protein. This additional quantity of water makes the encapsulated product both difficult and not economical to dry. The resulting product, when dried, exhibits poor physical protection of the lipid material. If the emulsion is allowed to set to let the air escape before the addition of acid or other protein denaturing agent, then the droplets join together and the lipid separates from the protein. Large droplets formed under these conditions are fragile and break down easily during storage and drying, which makes an inferior quality and commercially impractical product.
Well-known methods are described in the literature indicating the use of alkalis and acids to modify the secondary and tertiary structures of proteins without hydrolyzing the primary or peptide bond. As the pH approaches the isoelectric point of the protein, it will "clump" or fold up in a denatured state. Also, it is common knowledge that proteins are made of amino acids of which some are hydrophobic and some are hydrophilic. If protein in a lipid/water mixture is treated with an amount of base necessary to break down the secondary and tertiary structure of the protein but not with an amount which will break the primary links between the amino acids (i.e., the backbone of the protein or peptide bonds), then the hydrophobic amino acid side chains can orientate toward the lipid phase and the hydrophilic side chains can orientate toward the aqueous phase.
A stable capsule depends upon the formation of lipid droplets surrounded by protein in a manner in which hydrophilic amino acids are associated with water and hydrophobic amino acids are associated with lipid. The smaller the droplets, the more effective the encapsulation by the proteinaceous mixture. The mixture containing the lipid and alkali-treated protein requires shearing without the entrainment of air to produce droplets of a size which will be stable when the protein is denatured around the lipid. What is still needed is a method allowing formation of a stable capsule with good protection of the lipid material utilizing the least amount of exogenous chemicals.
Accordingly, it is an object of this invention to provide a process by which lipid material can be encapsulated by a protein material without entrainment of air into the dispersion by use of an in-line mixer in the process.
It is also an object of this invention to provide a process that allows determination of the best pH to provide a strong capsule and to minimize exogenous chemical use in the process.
It is another object of this invention to provide a process which allows addition of base during the process in a smooth, controlled and defined fashion allowing protein to denature without destroying the primary structure of the protein, specific for any selected protein source.
It is a further object of this invention to provide a process which allows addition of acid during the process in a smooth, controlled and defined fashion allowing protein to denature around lipid droplets while the droplets are still small and uniform in size, thereby improving the quality, stability and durability of the capsule and the final product.